CN117344329A - Oxygen-enriched vacancy ZnO catalyst electrode, preparation method thereof and application thereof in electrocatalytic reduction of nitrate nitrogen - Google Patents
Oxygen-enriched vacancy ZnO catalyst electrode, preparation method thereof and application thereof in electrocatalytic reduction of nitrate nitrogen Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 53
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 46
- 239000001301 oxygen Substances 0.000 title claims abstract description 46
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 46
- MMDJDBSEMBIJBB-UHFFFAOYSA-N [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] Chemical compound [O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH6+3] MMDJDBSEMBIJBB-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 238000002360 preparation method Methods 0.000 title claims abstract description 8
- 238000000034 method Methods 0.000 claims abstract description 15
- -1 zinc carboxylate Chemical class 0.000 claims abstract description 6
- 230000004913 activation Effects 0.000 claims abstract description 4
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 18
- 239000000243 solution Substances 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 13
- 239000002245 particle Substances 0.000 claims description 11
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 10
- 150000003751 zinc Chemical class 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 239000002244 precipitate Substances 0.000 claims description 8
- ONDPHDOFVYQSGI-UHFFFAOYSA-N zinc nitrate Chemical compound [Zn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ONDPHDOFVYQSGI-UHFFFAOYSA-N 0.000 claims description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 claims description 6
- 229910052739 hydrogen Inorganic materials 0.000 claims description 6
- 235000006408 oxalic acid Nutrition 0.000 claims description 6
- 238000009210 therapy by ultrasound Methods 0.000 claims description 6
- 239000000853 adhesive Substances 0.000 claims description 4
- 230000001070 adhesive effect Effects 0.000 claims description 4
- 238000001354 calcination Methods 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 4
- 238000000576 coating method Methods 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 4
- 238000001914 filtration Methods 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 230000002441 reversible effect Effects 0.000 claims description 4
- 239000012266 salt solution Substances 0.000 claims description 4
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 claims description 4
- 229920000557 Nafion® Polymers 0.000 claims description 3
- BJEPYKJPYRNKOW-REOHCLBHSA-N (S)-malic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O BJEPYKJPYRNKOW-REOHCLBHSA-N 0.000 claims description 2
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 claims description 2
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 claims description 2
- BJEPYKJPYRNKOW-UHFFFAOYSA-N alpha-hydroxysuccinic acid Natural products OC(=O)C(O)CC(O)=O BJEPYKJPYRNKOW-UHFFFAOYSA-N 0.000 claims description 2
- 235000015165 citric acid Nutrition 0.000 claims description 2
- 238000011068 loading method Methods 0.000 claims description 2
- 235000011090 malic acid Nutrition 0.000 claims description 2
- 239000001630 malic acid Substances 0.000 claims description 2
- 239000000758 substrate Substances 0.000 claims description 2
- 239000011975 tartaric acid Substances 0.000 claims description 2
- 235000002906 tartaric acid Nutrition 0.000 claims description 2
- 238000005406 washing Methods 0.000 claims description 2
- 235000005074 zinc chloride Nutrition 0.000 claims description 2
- 239000011592 zinc chloride Substances 0.000 claims description 2
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 claims description 2
- 229960001763 zinc sulfate Drugs 0.000 claims description 2
- 229910000368 zinc sulfate Inorganic materials 0.000 claims description 2
- 150000001735 carboxylic acids Chemical class 0.000 claims 5
- 229910002651 NO3 Inorganic materials 0.000 abstract description 16
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 abstract description 16
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 abstract description 13
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 abstract description 10
- 230000000694 effects Effects 0.000 abstract description 10
- 229910021529 ammonia Inorganic materials 0.000 abstract description 5
- 239000013067 intermediate product Substances 0.000 abstract description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 239000011701 zinc Substances 0.000 abstract description 3
- 238000009388 chemical precipitation Methods 0.000 abstract description 2
- 239000002243 precursor Substances 0.000 abstract description 2
- 238000001179 sorption measurement Methods 0.000 abstract description 2
- 229910052725 zinc Inorganic materials 0.000 abstract description 2
- 238000006243 chemical reaction Methods 0.000 description 18
- 239000000463 material Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 8
- 239000000047 product Substances 0.000 description 6
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- ZPEJZWGMHAKWNL-UHFFFAOYSA-L zinc;oxalate Chemical compound [Zn+2].[O-]C(=O)C([O-])=O ZPEJZWGMHAKWNL-UHFFFAOYSA-L 0.000 description 4
- 238000009826 distribution Methods 0.000 description 3
- 235000019441 ethanol Nutrition 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 238000003917 TEM image Methods 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000003755 preservative agent Substances 0.000 description 2
- 230000002335 preservative effect Effects 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 239000010865 sewage Substances 0.000 description 2
- 238000000967 suction filtration Methods 0.000 description 2
- 239000002352 surface water Substances 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 108010061951 Methemoglobin Proteins 0.000 description 1
- 208000015914 Non-Hodgkin lymphomas Diseases 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005341 cation exchange Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 201000010099 disease Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 239000003651 drinking water Substances 0.000 description 1
- 235000020188 drinking water Nutrition 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000012851 eutrophication Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000003337 fertilizer Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000003673 groundwater Substances 0.000 description 1
- 239000010842 industrial wastewater Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- YPJKMVATUPSWOH-UHFFFAOYSA-N nitrooxidanyl Chemical compound [O][N+]([O-])=O YPJKMVATUPSWOH-UHFFFAOYSA-N 0.000 description 1
- 150000002926 oxygen Chemical class 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000011550 stock solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
- C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
- C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
- C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
- C25B11/077—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the compound being a non-noble metal oxide
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
- C02F1/46109—Electrodes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/27—Ammonia
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
- C02F1/46104—Devices therefor; Their operating or servicing
- C02F1/46109—Electrodes
- C02F2001/46133—Electrodes characterised by the material
- C02F2001/46138—Electrodes comprising a substrate and a coating
- C02F2001/46142—Catalytic coating
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
- C02F2101/163—Nitrates
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Inorganic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Catalysts (AREA)
Abstract
The invention discloses an oxygen-enriched vacancy ZnO catalyst electrode, a preparation method thereof and application thereof in electrocatalytic reduction of nitrate nitrogen. According to the invention, zinc carboxylate synthesized by a chemical precipitation method is used as a precursor to calcine to generate ZnO, and then a large number of oxygen vacancies are generated by electroreduction and activation, so that the adsorption of nitrate nitrogen and intermediate products thereof is enhanced, the activity of electrocatalytic reduction of nitrate and the selectivity of ammonia nitrogen can be effectively improved, and the ammonia production effect is better.
Description
Technical Field
The invention belongs to the technical field of electrochemistry, and particularly relates to an oxygen-enriched vacancy ZnO catalyst electrode, a preparation method thereof and application thereof in electrocatalytic reduction of nitrate nitrogen.
Background
Nitrate nitrogen is widely present in surface and ground water, where surface water nitrate nitrogen is mainly derived from industrial wastewater, domestic sewage and agricultural sewage. The high concentration of nitrate in water can cause eutrophication of water body, reduce available oxygen of aquatic organisms and destroy aquatic ecosystem. And the nitrate nitrogen in the drinking water exceeds standard, and diseases such as methemoglobin hematopathy, non-Hodgkin lymphoma and the like can be caused, wherein the electrocatalytic reduction Nitrate (NRR) technology has the characteristics of high efficiency, no pollution, simple reaction condition and the like, and more importantly, one of main products of the reaction is ammonia nitrogen, so that the reduction of the nitrate nitrogen to the ammonia nitrogen can be realized for recycling. Ammonia is one of the most valuable chemical products in the world, being a good nitrogen source and green hydrogen-rich material for fertilizers.
The research of catalyst materials in the electrocatalytic reduction of nitrate nitrogen technology is currently the focus. Current research is focused mainly on copper-based catalysts, with less research on other metals and their metal oxides.
Disclosure of Invention
In view of the above, the invention aims to provide an oxygen-enriched vacancy ZnO catalyst electrode, a preparation method thereof and application thereof in electrocatalytic reduction of nitrate nitrogen, which can effectively improve the activity of electrocatalytic reduction of nitrate and the selectivity of ammonia nitrogen.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the invention provides a preparation method of an oxygen-enriched vacancy ZnO catalyst electrode, which comprises the following steps:
(1) Dissolving zinc salt in water to obtain zinc salt solution, dissolving organic carboxylic acid in water to obtain organic carboxylic acid solution, and then dropwise adding the organic carboxylic acid solution into the zinc salt solution to obtain carboxylic acid zinc salt precipitate;
(2) Filtering, washing and drying the carboxylic acid zinc salt precipitate obtained in the step (1), and calcining in the air atmosphere to obtain ZnO particles;
(3) And (3) loading the ZnO particles obtained in the step (2) on an electrode substrate to prepare an electrode, and then performing electroreduction activation on the electrode to make the surface of the electrode rich in oxygen vacancies, thereby obtaining the oxygen-enriched vacancy ZnO catalyst electrode.
In the preferred technical scheme, in the step (1), the zinc salt is one or more of zinc chloride, zinc sulfate and zinc nitrate.
In the preferred technical scheme, in the step (1), the organic carboxylic acid is one or more of malic acid, citric acid, oxalic acid and tartaric acid.
In the preferred technical scheme, in the step (1), the molar ratio of the zinc salt to the organic carboxylic acid is 1.0-4.0:1.
In the step (2), the calcination temperature is 250-450 ℃.
As a preferable technical scheme, the specific method of the step (3) is as follows: adding ZnO particles and carbon powder into isopropanol and ethanol solution for mixing, adding Nafion as an adhesive, and performing ultrasonic treatment until uniform ink is formed; under the heating of an infrared lamp, uniformly coating the catalyst ink on two sides of carbon paper to serve as a working electrode; the working electrode is activated for 15.0min under the hydrogen reversible electrode of-0.65V vs. to make the surface of the working electrode rich in oxygen vacancies, thus obtaining the oxygen-enriched vacancy ZnO catalyst electrode.
The invention also provides the oxygen-enriched vacancy ZnO catalyst electrode prepared by the preparation method.
The invention also provides application of the oxygen-enriched vacancy ZnO catalyst electrode in electrocatalytic reduction of nitrate nitrogen, and the working voltage is preferably-0.65V.
The invention has the beneficial effects that:
according to the invention, zinc carboxylate synthesized by a chemical precipitation method is used as a precursor to calcine to generate ZnO, and then a large number of oxygen vacancies are generated by electroreduction and activation, so that the adsorption of nitrate nitrogen and intermediate products thereof is enhanced, the activity of electrocatalytic reduction of nitrate and the selectivity of ammonia nitrogen can be effectively improved, and the ammonia production effect is better.
Drawings
In order to make the objects, technical solutions and advantageous effects of the present invention more clear, the present invention provides the following drawings for description:
FIG. 1 is a TEM image of an oxygen-enriched vacancy ZnO catalyst electrode prepared in example 1.
FIG. 2 is an XPS plot of the oxygen-enriched vacancy-ZnO catalyst electrode prepared in example 1 and the ZnO catalyst electrode prepared in comparative example 1.
FIG. 3 is a graph showing the distribution of nitrate nitrogen and products over time in the electrocatalytic reduction of nitrate by the oxygen-enriched vacancy ZnO catalyst electrode prepared in example 1.
Fig. 4 is a graph showing the distribution of nitrate nitrogen and products over time in the electrocatalytic reduction of nitrate by the ZnO catalyst electrode prepared in comparative example 1.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to limit the invention, so that those skilled in the art may better understand the invention and practice it.
The methods used in the following examples are conventional methods unless otherwise specified. The materials or reagents required in the examples below are commercially available unless otherwise specified.
Example 1: oxygen-enriched vacancy ZnO catalyst electrode
(1) Respectively 5mmolZn (NO) 3 ) 2 And 5mmol of oxalic acid (H) 2 C 2 O 4 ) Dissolving in 100.0mL of water, and performing ultrasonic treatment until the solution is completely dispersed; adding oxalic acid solution into zinc nitrate solution dropwise at a constant speed at a rotating speed of 200rpm, wherein the process takes 20.0min to obtain zinc oxalate precipitate, and sealing the preservative film and standing for 2.0h;
(2) Filtering the zinc oxalate precipitate obtained in the step (1) by using a suction filtration device, cleaning the obtained material by using absolute ethyl alcohol, uniformly paving the material in a crucible, placing the crucible in an oven for drying at 60 ℃ for 1.0h, and then burning the material for 6h at 350 ℃ at a heating rate of 5 ℃/min in an air atmosphere to obtain ZnO particles;
(3) Weighing ZnO particles and 3mg of carbon powder in the step (2), adding 0.4mL of isopropyl alcohol and 3mL of ethanol solution for mixing, adding 20 mu LNafion as an adhesive, and performing ultrasonic treatment until uniform ink is formed; under the heating of an infrared lamp, uniformly coating the catalyst ink on two sides of carbon paper to serve as a working electrode; the working electrode is activated for 15.0min under the condition of minus 0.65V vs. RHE (hydrogen reversible electrode) to make the surface of the working electrode rich in oxygen vacancies, thus obtaining the oxygen-enriched vacancy ZnO catalyst electrode.
Comparative example 1: znO catalyst electrode
(1) Respectively, 5mmol Zn (NO) 3 ) 2 And 5mmol of oxalic acid (H) 2 C 2 O 4 ) Dissolving in 100.0mL of water, and performing ultrasonic treatment until the solution is completely dispersed; adding oxalic acid solution into zinc nitrate solution dropwise at a constant speed at a rotating speed of 200rpm, wherein the process takes 20.0min to obtain zinc oxalate precipitate, and sealing the preservative film and standing for 2.0h;
(2) Filtering the zinc oxalate precipitate obtained in the step (1) by using a suction filtration device, cleaning the obtained material by using absolute ethyl alcohol, uniformly paving the material in a crucible, placing the crucible in an oven for drying at 60 ℃ for 1.0h, and then burning the material for 6h at 350 ℃ at a heating rate of 5 ℃/min in an air atmosphere to obtain ZnO particles;
(3) Weighing ZnO particles and 3mg of carbon powder in the step (2), adding 0.4mL of isopropyl alcohol and 3mL of ethanol solution for mixing, adding 20 mu L of Nafion as an adhesive, and performing ultrasonic treatment until the mixture forms uniform ink; and (3) uniformly coating the catalyst ink on two sides of the carbon paper under the heating of an infrared lamp to obtain the ZnO catalyst electrode.
A TEM image of the oxygen-enriched vacancy ZnO catalyst electrode prepared in example 1 is shown in FIG. 1, from which uniform ZnO particles can be seen.
XPS plots of the oxygen-enriched vacancy ZnO catalyst electrode prepared in example 1 and the ZnO catalyst electrode prepared in comparative example 1 are shown in FIG. 2, from which it can be seen that a large number of oxygen vacancies have occurred in the activated oxygen-enriched vacancy ZnO catalyst.
Example 2: removal effect of ZnO catalyst electrode on pollutant nitrate radical
(1) The construction of the denitration reaction device comprises the following specific steps:
a) The denitration reaction electrolyzer is an H-type electrolyzer. The anode chamber and the cathode chamber are separated by a cation exchange membrane (Nafion-117), the volumes of the anode chamber and the cathode chamber are 150mL, sodium sulfate (50 mM) is respectively added into the anode chamber and the cathode chamber as electrolyte, the volumes are 100mL, and nitrogen is required to be introduced for 10min before the reaction; then adding a nitrate nitrogen stock solution with an initial concentration of 100mg/L into a cathode electrolytic chamber by using a 1mL pipette, and adding a B-type magnetic stirrer for stirring;
b) According to the three-electrode system principle, a circuit of the electrocatalytic denitration device is built, wherein a counter electrode is a platinum sheet electrode (30 mm multiplied by 30 mm), a reference electrode is a reversible hydrogen electrode, and a working electrode is respectively an oxygen-enriched vacancy ZnO catalyst electrode prepared in the example 1 and a ZnO catalyst electrode prepared in the comparative example 1;
c) Evaluation of denitration reaction effect, concentration of contaminants, intermediate products and final products was detected by a gas ultraviolet spectrophotometer (UV 1000).
(2) The operation of the denitration reaction device comprises the following steps:
a) The whole denitration experiment device is placed in a constant-temperature water bath magnetic stirrer at 25 ℃, the stirring speed is 400rpm, and uniform stirring is kept;
b) Setting electrochemical workstation parameters, selecting a timing ampere method program, setting the voltage to be-0.65V, and starting an electrocatalytic reduction nitrate reaction program.
(3) The denitration reaction activity is determined as follows:
a) When the reaction was carried out for 0min, 60min, 120min, 180min, and 240min, samples (about 2.5 ml) were taken from the reaction solution in the cathode chamber using a glass syringe, and 1ml of the samples were removed and the volume was fixed to 25ml in a cuvette.
b) Measuring the concentration of nitrate nitrogen, ammonia nitrogen and nitrate nitrogen at wavelengths of 220nm, 420nm and 540nm respectively by using an ultraviolet spectrophotometer (UV 1000);
c) Nitrate removal rate (η) = (1-C) t /C 0 )*100％；
Selectivity S of Ammonia nitrogen NH4+ Expressed as: s is S NH4+ ＝C NH4+ /(C 0 -C t )*100％；
Wherein C is NH4+ Representing NH after t time of electrolysis 4 + Concentration of-N (mg L) -1 ) C0 represents NO 3 - Initial concentration of-N (mg L -1 ) The method comprises the steps of carrying out a first treatment on the surface of the Ct represents time t NO 3 - Concentration of-N (mg L) -1 )。
The working electrode adopts the oxygen-enriched vacancy ZnO catalyst electrode prepared in example 1 and the ZnO catalyst electrode prepared in comparative example 1 respectively, and the electrocatalytic reduction nitrate reaction is carried out according to the steps, and the distribution of nitrate nitrogen and products in the electrocatalytic reduction nitrate reaction is shown in the graphs of fig. 3 and 3As shown in fig. 4, the results show: when the oxygen-enriched vacancy ZnO catalyst electrode prepared in example 1 was used as a working electrode, the removal rate of nitrate nitrogen was continuously increased, and after 4 hours of reaction, the removal rate reached 99.6%, NH 3 Has a selectivity of 92.2%. Under the same conditions, when the oxygen-enriched vacancy ZnO catalyst electrode prepared in comparative example 1 is used as a working electrode, the removal rate is 99.5 percent, and NH is removed 3 The selectivity of (2) was 62.2%. The oxygen-enriched vacancy ZnO catalyst electrode prepared in example 1 is proved to have higher activity and ammonia production selectivity than the ZnO catalyst electrode prepared in comparative example 1.
The working electrode was prepared by using the oxygen-enriched vacancy ZnO catalyst electrode prepared in example 1, performing electrocatalytic reduction of nitrate by the above steps, and changing the conditions of voltage setting to-0.5V, -0.55V, -0.6V, -0.65V, -0.7V, -0.75V, -0.8V, respectively, and performing 7 times of reactions. The result of the electrocatalytic reduction of nitrate by the oxygen-enriched vacancy ZnO catalyst electrode under different voltages is shown in the table 1, the selectivity of ammonia nitrogen gradually increases with the increase of the voltage to-0.65V, and the selectivity of ammonia nitrogen is reduced to a certain extent due to the enhancement of the hydrogen evolution side reaction with the continuous increase of the voltage.
TABLE 1 removal of oxygen-enriched vacancy ZnO catalyst electrode nitrate and selectivity of ammonia nitrogen at different voltages
| Voltage (V) | -0.50 | -0.55 | -0.60 | -0.65 | -0.70 | -0.75 | -0.80 |
| Removal efficiency (. Eta.) | 99.8 | 99.6 | 99.4 | 99.6 | 99.2 | 99.7 | 99.6 |
| Ammonia nitrogen selectivity (S)% | 52.1 | 77.9 | 85.46 | 92.2 | 95.8 | 93.3 | 89.1 |
The working electrode adopts the oxygen-enriched vacancy ZnO catalyst electrode prepared in the embodiment 1, the electrocatalytic reduction nitrate reaction is carried out according to the steps, and the reaction is repeated for 5 times, and the result is shown in the table 2, and the ammonia nitrogen selectivity of the 5 repeated reactions is about 90%, which indicates that the stability and the repeatability of the oxygen-enriched vacancy ZnO catalyst electrode are better.
TABLE 2 removal efficiency and Ammonia Selectivity for 5 repeated reactions with the same electrode
| Nitrate concentration (mg/L) | 1 | 2 | 3 | 4 | 5 |
| Removal efficiency (. Eta.) | 84.71 | 97.26 | 97.40 | 95.70 | 91.47 |
| Ammonia nitrogen selectivity (S)% | 100 | 88.22 | 85.44 | 90.34 | 92.24 |
The above-described embodiments are merely preferred embodiments for fully explaining the present invention, and the scope of the present invention is not limited thereto. Equivalent substitutions and modifications will occur to those skilled in the art based on the present invention, and are intended to be within the scope of the present invention. The protection scope of the invention is subject to the claims.
Claims (9)
1. A preparation method of an oxygen-enriched vacancy ZnO catalyst electrode is characterized by comprising the following steps: the method comprises the following steps:
(1) Dissolving zinc salt in water to obtain zinc salt solution, dissolving organic carboxylic acid in water to obtain organic carboxylic acid solution, and then dropwise adding the organic carboxylic acid solution into the zinc salt solution to obtain carboxylic acid zinc salt precipitate;
(2) Filtering, washing and drying the carboxylic acid zinc salt precipitate obtained in the step (1), and calcining in the air atmosphere to obtain ZnO particles;
(3) And (3) loading the ZnO particles obtained in the step (2) on an electrode substrate to prepare an electrode, and then performing electroreduction activation on the electrode to make the surface of the electrode rich in oxygen vacancies, thereby obtaining the oxygen-enriched vacancy ZnO catalyst electrode.
2. The method for preparing the oxygen-enriched vacancy ZnO catalyst electrode according to claim 1, wherein: in the step (1), the zinc salt is one or more of zinc chloride, zinc sulfate and zinc nitrate.
3. The method for preparing the oxygen-enriched vacancy ZnO catalyst electrode according to claim 1, wherein: in the step (1), the organic carboxylic acid is one or more of malic acid, citric acid, oxalic acid and tartaric acid.
4. The method for preparing the oxygen-enriched vacancy ZnO catalyst electrode according to claim 1, wherein: in the step (1), the molar ratio of the zinc salt to the organic carboxylic acid is 1.0-4.0:1.
5. The method for preparing the oxygen-enriched vacancy ZnO catalyst electrode according to claim 1, wherein: in the step (2), the calcination temperature is 250-450 ℃.
6. The method for preparing the oxygen-enriched vacancy ZnO catalyst electrode according to claim 1, wherein: the specific method of the step (3) is as follows: adding ZnO particles and carbon powder into isopropanol and ethanol solution for mixing, adding Nafion as an adhesive, and performing ultrasonic treatment until uniform ink is formed; under the heating of an infrared lamp, uniformly coating the catalyst ink on two sides of carbon paper to serve as a working electrode; the working electrode is activated for 15.0min under the hydrogen reversible electrode of-0.65V vs. to make the surface of the working electrode rich in oxygen vacancies, thus obtaining the oxygen-enriched vacancy ZnO catalyst electrode.
7. An oxygen-enriched vacancy ZnO catalyst electrode prepared by the method of any one of claims 1 to 6.
8. Use of the oxygen-enriched vacancy ZnO catalyst electrode of claim 7 for electrocatalytic reduction of nitrate nitrogen.
9. The use according to claim 8, characterized in that: the operating voltage was-0.65V.
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